The Brief Electricity and Magnetism Assessment (BEMA) is a multiple-choice instrument commonly used to measure introductory undergraduate students' conceptual understanding of electricity and magnetism. This study used a network analysis technique called modified module analysis-partial (MMA-P) to identify clusters of correlated responses, also known as communities, within 12214 BEMA responses. MMA-P identifies both communities related to the structure of the instrument and communities related to incorrect student reasoning. Every community resulting from MMA-P came from blocked items; groups of items that all refer to the same physical system. The most prevalent and consistently selected incorrect answers involved the relation of the electric field to the electric potential difference. The community structure identified in the Conceptual Survey of Electricity and Magnetism (CSEM) by a prior MMA-P study on items shared by the CSEM and BEMA differed because of the different incorrect responses available in the two instruments. One pair of items in the BEMA involving the induced electric field by a changing magnetic field showed evidence of students applying a variety of incorrect models; the scores on these items indicate their inclusion in the instrument should be reconsidered.